Upgrading Mist on Ubuntu

1. Backup your keystore (/.ethereum/keystore)
2. Backup your data folder (/.config/Mist)
3. Download the latest zip from here and install.

For more information on backing up wallets, see here: How to backup mist wallets?

Upgrading go-ethereum:

sudo apt-get install software-properties-common
sudo add-apt-repository -y ppa:ethereum/ethereum
sudo add-apt-repository -y ppa:ethereum/ethereum-dev
sudo apt-get update
sudo apt-get upgrade

or simply build the git repository.

git clone https://github.com/ethereum/go-ethereum
cd go-ethereum  # (use "git checkout <branch>" to switch to branches or tag/commit. ex: git checkout -f tags/v1.10.16)
make geth       # (to build geth binary in build/bin)
make clean      # (clean things up, if you want to build a different branch or commit)
sudo cp build/bin/geth /usr/local/bin/

Mist starts its own geth process, which uses the same default chaindata database location as the geth client you run manually. When you start the geth client first, it acquires a lock on the database files and prevents Mist from accessing them.

If you need to run both of them simultaneously, use a separate data directory for geth by starting it with --datadir option.